This invention relates to a flexible printed circuit base material, and provides a printed circuit board material which has a low dielectric constant and also is flexible.
Providing flexibility to materials used for printed circuit boards results in enhancement of the freedom of design of such systems because printed circuit boards made of a flexible material can be installed in limited spaces, particularly in bent gaps, for example, and can be installed in places having varied shapes. In recent years, because achievements serving to reduce wall thicknesses and overall dimensions of electronic devices are profoundly important, flexible materials have been finding utility in a growing range of applications.
Heretofore, polyimide resin and polyester resin have been used as flexible materials for printed circuit boards. In recent years, such super-high speed elements as gallium arsenide IC's have been developed. To permit manufacture of devices of high operating speed by the use of such elements, the materials used for the production of their printed circuit boards are required to have low dielectric constants. To meet this requirement, a material made of bismaleimide-triazine resin has found utility in printed circuit boards.
Polyimide resin and polyester resin for printed circuit board applications have fairly large dielectric constants, falling on the order of 3.5 to 4.0 (at 1 MHz) and are generally not capable of meeting the aforementioned requirements, resulting in a need for development of devices having high operating speed for use in such super-high-speed elements mentioned above.
The material using the aforementioned bismaleimide-triazine resin has a low dielectric constant and, therefore, is capable of meeting the requirement directed to the development of devices having high operating speed. This resin heretofore generally could be used only as a rigid material. It cannot be molded easily in the shape of a thin film. Since it cannot easily assume flexibility, the needed material having high freedom of design mentioned above cannot be obtained from this resin alone.